The present invention is related to a method of depositing a zinc oxide coating on a transparent substrate. More particularly, it is related to a chemical vapor deposition method of depositing a zinc oxide coating on a transparent substrate which coating is modified to create a zinc oxide coating having a combination of desired properties.
Growth of zinc oxide coatings by CVD has been reported in the scientific literature. For example, Smith, Frank T. J., “Metalorganic chemical vapor deposition of oriented ZnO films over large areas”, Applied Physics Letters, Vol. 43, No. 12 (1983) pg. 1108-1110, describes a metal organic chemical vapor deposition process for preparing c-axis-oriented ZnO films in a system similar to that which is commercially available for SiO2 deposition. The resulting films are said to be highly uniform in thickness and to adhere to a variety of substrates.
Gerfin and Dahmen in CVD of Nonmetals (W. S. Rees, Jr. ed., VCH Publishers, Inc., New York, N.Y., 1996), chapter 3, pg. 180-185, describe the work of a number of researchers regarding the use of a variety of chemical preparation techniques to form zinc oxide films. Use of dialkyl zinc compounds and various oxygen-containing compounds is discussed.
Deposition of zinc oxide films has also been described in the patent literature.
U.S. Pat. No. 4,751,149 to Vijaykumar, P., et al. describes a low temperature (200° C. or less) low pressure (2 torr or less) static deposition method for zinc oxide films, utilizing an organozinc compound and water carried in an inert gas. The resulting zinc oxide film is said to have a low resistivity which can be varied by addition of a Group 13 element.
U.S. Pat. No. 4,990,286 to Gordon, R., et al. describes deposition of fluorine-doped zinc oxide films by chemical vapor deposition from vapor mixtures of zinc, oxygen and fluorine-containing compounds. The films produced are said to be highly electrically conductive, transparent to visible light, reflective to infrared radiation, and absorbing to ultraviolet light. Temperature sensitive substrates are said to be suitable with the process of the subject invention.
U.S. Pat. No. 5,306,522 describes processes for coating a substrate, in particular, substrates including shielded surfaces, coated with zinc oxide containing coatings. The described processes include the elements of contacting a substrate with a zinc oxide precursor, preferably maintaining the precursor coated substrate at conditions to equilibrate the coating, then oxidizing the precursor to form a coating containing zinc oxide. The substrates coated by the process for use in various applications, are also described.
U.S. Pat. No. 5,407,743, which is related to the above-mentioned U.S. Pat. No. 5,306,522, includes additional information related particularly to the zinc oxide coated articles made by the described process.
U.S. Pat. No. 6,416,814 to Giolando, D. describes the use of ligated compounds of tin, titanium, and zinc as metal oxide precursor compounds in a method to produce high quality metal oxide coatings when coming in contact with a heated substrate.
Durable, coated transparent substrate materials are increasingly in demand. It would be desirable to have zinc oxide coated transparent substrate materials exhibiting high visible light transmittance, low emissivity properties and/or solar control properties, high electrical conductivity/low sheet resistance, and which could be manufactured cost effectively.